The invention relates to a method of spinning-in yarn on an operating unit of a rotor spinning machine which comprises steps of yarn preparation for spinning-in, steps of spinning rotor preparation for spinning-in, and final spinning-in steps. The steps of yarn preparation for spinning-in comprise at least the detection of the yarn end on the bobbin or the preparation of auxiliary yarn when spinning-in on an empty tube, unwinding and metering a yarn length required for spinning-in, setting the yarn into its spinning-in position on the operating unit of the rotor spinning machine in which the yarn is outside the reach of the yarn distributor and not clamped between the rollers of the draw-off mechanism, creating the spinning-in yarn end and introducing it into the yarn delivery tube from the spinning rotor. The step of the spinning rotor preparation for the spinning-in comprise at least the opening of the spinning unit, cleaning of the spinning rotor, closing of the spinning unit. The final spinning-in steps comprise at least the beginning of the sliver supply to the singling-out device, leading of the fibres from the singling-out device away from the spinning rotor for a predetermined time interval, bringing the spinning-in yarn end into contact with the collecting groove of the spinning rotor and starting of the yarn draw-off and winding.
The invention also relates to a device for carrying out the yarn spinning-in on a rotor spinning machine wherein each operating unit comprises a spinning unit with a cover adapted to be opened for gaining access to the spinning rotor for its cleaning.
Depending on the method of the yarn spinning-in, rotor spinning machines are divided into two groups, and more exactly, into machines with manual spinning-in and machines with automated spinning-in by means of an attending device traveling along the operating units of the machine.
Rotor spinning machines with manual spinning-in are equipped with an auxiliary spinning-in device on each operating unit so that the operator carries out only the steps of yarn preparation for the spinning-in and cleaning of the spinning rotor including the opening and closing of the spinning unit and introducing the spinning-in yarn end into the yarn delivery tube. In former machine types, the operator manually lets the spinning-in yarn end sink onto the collecting groove and manually sets in action the auxiliary spinning-in device which then mechanically or electrically actuates the sliver feed, yarn draw-off and yarn winding on the bobbin.
In more modern machine types, the operator carries out manually the same steps as in the former machine types except the sinking of the spinning-in yarn end on the collecting groove of the spinning rotor. The operator just introduces the spinning-in yarn end into the yarn delivery tube and prepares the yarn into the preparatory position for spinning-in in which the spinning-in yarn end is held by adequate means of the operating unit of the machine ready to be sunk onto the collecting groove of the spinning rotor. As disclosed in CZ 284295 B5, at each operating unit the arms of the winding device and the pressure lever of the delivery device are coupled with a control electromagnet interconnected with a control unit which is coupled also with a deflecting member intended to deflect the yarn from its operative course and to sink the spinning-in yarn end onto the collecting groove of the spinning rotor, with a sliver feeding device, and with a monitor for testing the quality and/or the presence of the yarn. At a command given by the operator, the control unit sets in mutually timed action all the above spinning-in means of the operating unit. This device has led to a substantial improvement in the piecer quality since the spinning-in operations proper are carried out by the means of the operating unit of the machine with elimination of the operator""s influence.
In spite of the considerable improvement in the quality, neither the size nor the strength of the piecers is constant, and the final yarn producers are interested in improved piecer quality.
In automated spinning machines, the attending device is responsible for all steps connected with the resumption of the spinning-in process. The timing of the individual steps of the attending device is controlled electronically and the start moment of each spinning-in step can be within certain limits modified as needed.
To increase the piecer quality, automatic spinning machines are equipped with an attending device controlled means for delivering the sliver from the singling-out device away from the spinning rotor before the spinning start. The means for the sliver delivery from the singling-out device away from the spinning rotor can contain pressure air supply from the attending device acting onto the circumference of the rotating combing roller of the singling-out device as described in CZ 280036 or sucking off of the fibres from the singling-out device behind the channel for fibre supply into the spinning rotor controlled and carried out by the attending device, as described in the CZ patent application 1995-255 and U.S. Pat. No. 5,535,580.
Automated rotor spinning machines give good piecer quality but the attending devices are very complicated and expensive and each highly productive machine requires a number of them which complicates the attendance and further increases the purchase cost.
The invention aims at reducing the attendance time required for the spinning-in operation on an operating unit.
Objects and advantages of the invention will be set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
The increase in the piecer quality and the reduction of the attendance time required for the spinning-in operation on an operating unit is obtained by the method according to the invention whose principle consists in that at least some of the final spinning-in steps are timed in relation to the closing of the spinning unit thus obtaining optimum piecer quality repeatedly at all operating units of the machine
In manually operated machines, the method according to the invention eliminates the operator""s intervention into the process proper of attaching the yarn at the resumption of spinning and permits exactly the synchronization (timing) of the final spinning-in steps, this timing being on all operating units repeatedly (invariably) the same. In automated rotor spinning machines, this method permits reduction of the attendance interval of the attending device.
According to the specific technological requirements of a given case, imposed either by the machine or by the yarn in question, the timing can be carried out in relation to the moment when the closing of the spinning unit has ended, has begun, or has reached a predetermined moment in the course of the closing operation of the spinning unit.
The choice of a suitable beginning of the timing of the final spinning-in steps and the possibility of combining the timing moments for the individual specific final spinning-in steps increase the variants of use of the method according to the invention.
To realize the method according to the invention, it is advantageous if, depending on the beginning of the closing of the spinning unit, the yarn delivery from the singling-out device away from the spinning rotor starts first followed in timed relation to the completed closing of the spinning unit by the beginning/start of the sliver feed into the singling-out device, the termination of the yarn deflection outside/away from the spinning rotor, letting the spinning-in yarn end come onto the collecting groove of the spinning rotor, and starting the yarn delivery and winding.
The yarn delivery during the closing process of the spinning unit prior to the spinning rotor start appears to be the most favourable variant.
The start of the fibre delivery prior to the closing of the spinning unit and prior to the start of further final spinning-in steps will ensure that no fibres or impurities enter the spinning rotor prior to the spinning-in, and the following timing of further final spinning-in steps in relation to the completed closing of the spinning unit ensures repeatedly (invariably) constant condition for spinning-in on all operating units while the moment of the sliver feed start, that of the termination of the fibre delivery from the singling-out device outside the spinning rotor, that of letting the spinning-in yarn end come onto the collecting groove of the spinning rotor, and that of the yarn winding can be to a required extent adjusted in accordance with the specific technological requirements imposed upon the yarn being spun.
In particular, in manually attended machines with manual closing of the spinning unit, it is advantageous if the steps of the yarn preparation for spinning-in and the steps of the spinning rotor preparation including the closing of the spinning unit are carried out manually whereas the final spinning-in steps, synchronized in relation to the closing process of the spinning unit, are carried out by the means of the operating unit of the machine and are started by the closing process of the spinning unit.
In another variant of the method according to the invention, it is advantageous if the steps of the yarn preparation for spinning-in and the steps of the spinning rotor preparation for spinning-in, except the closing of the spinning unit and the final spinning-in steps, are carried out by the means of the operating unit of the machine, the closing process being initiated by an operator""s command, and the final spinning-in steps by the closing process of the spinning unit. This enables the manually attended machines to reach the piecer quality equal or even superior to that of present-day automated machines since the means of the attending device in many cases fail to ensure a perfect fibre delivery from the singling-out device outside the spinning rotor prior to the closing of the spinning unit.
In automated rotor spinning machines, it is advantageous to use the means of the attending device for carrying out the steps of the yarn spinning-in, including the closing process of the spinning unit, and the means of the operating unit of the machine, for carrying out the final spinning-in steps initiated by the closing process of the spinning unit.
In another variant of the method suitable for automated rotor spinning machine, the means of the operating unit of the machine carry out the spinning-in preparatory steps both of yarn and of the spinning rotor except the closing or, as the case may be, also the opening of the spinning unit, as well as the final spinning-in steps, the closing process of the spinning unit being initiated by a command from the attending device, and the timed (synchronized) spinning-in steps being initiated by the closing process of the spinning unit.
In automated rotor spinning machines, this solution permits reduction of the attendance time interval required for the spinning-in operation at an operating unit since the attending device can leave the operating unit being attended, in the first variant after the completed closing of the spinning unit, and in the second variant after the beginning of the closing process of the spinning unit initiated by it (by the attending device). Besides the reduction in the length of the attending time, the attending device is rendered simpler and cheaper, and the piecer quality is superior to that reached by some attending devices, since optimum conditions of fibre delivery from the singling-out device outside the spinning rotor prior to the completed closing of the spinning unit, i.e., prior to the rotor rotation start can be ensured in every case.